Apparatus and method for removing piping from the ground

Abstract: Apparatus for removing piping from the ground comprises a cable (1) which has pipe engaging means (2) disposed along its length. The pipe engaging means (2) are arranged such that the cable (1) is insertable into a pipe (3) in one direction but that attempted withdrawal of the cable (1) in the opposite direction relative to the pipe (3) causes the pipe engaging means (2) to jam the cable (1) in the pipe (3). The pipe (3) can then be pulled from the ground, the pulling force being distributed along the length of the pipe (3).

Description: The present invention relates to an apparatus and method for removing piping from the ground, particularly, but not exclusively, lead or galvanised piping used in water distribution systems. In the past lead piping has been used extensively in water distribution systems. However, lead piping is no longer acceptable to such applications for health risk and environmental reasons. There is now an EEC directive related to the lead content of drinking water which will make it necessary to replace lead piping. Similarly, the corrosion of galvanised piping can present health risks and have an adverse effect on the environment and thus replacement of such piping with plastic piping is also desirable. Conventionally, lead pipes are extracted and replaced either by "trenching", i.e. digging down to expose the pipe then cutting it out and replacing it with plastic piping, or by "moling", i.e. using percussive moles to bore alongside the existing lead pipes while dragging in replacement plastic pipes. A combination of both "trenching" and "moling" can be used. Both of these methods of pipe removal/replacement have disadvantages. "Trenching" is time consuming, labour intensive and costly due to the requirement of removal of extracted thoroughfare material and also of filling up the trench (using stone etc.) to local authority requirements. Percussive moles are expensive pieces of equipment and also can be erratic and consequently may track off the desired path and either surface where they are not wanted, causing unwanted damage, or simply travel so far from the desired path that the pipe removal replacement operation must be stopped until the mole is found and dug out. "Moling" is thus a comparatively expensive operation and can involve time-consuming and expensive downtime and surface damage repair. There is also a possibility that when the mole veers off track it will damage other underground services. There are also existing methods of pipe removal which involve coupling the end of a cable to the pipe and dragging the pipe out of the ground using winch or other suitable machinery. A new pipe can be simultaneously dragged in position behind the old pipe. However, such existing methods have proved unsatisfactory. The cable is coupled to the pipe either by clamping the end of the cable to the front end of the pipe or by threading the cable through the pipe and clamping it to the rear end of the pipe. With the former method, the pipe may simply break in the location of the coupling under the strain of the pulling force and with the latter method, a length of pipe ahead of the coupling may simply distort when the pulling force is applied thereby rendering removal by this method difficult if not impossible. A method of pipe removal/replacement intended to overcome the above problems is proposed in International Patent Application No. WO92/10701. A wire rope is inserted through the pipe to be removed and then a settable bonding material is introduced into the pipe in the annular gap between the rope and the internal wall of the pipe. The bonding material is allowed to set thereby forming a bond between the rope and the pipe along the whole length of the pipe. The pipe is then removed from the ground via the pulling or pushing of the wire rope. The bond between the wire rope and the resin distributes the pulling/pushing force along the whole length of the pipe. This method is effective but suffers several disadvantages. The method is relatively difficult to implement and costly as the bonding material cannot be re-used, and the wire rope cannot be re-used unless the bonding material is first removed from it. It is an object of the present invention to obviate or mitigate the disadvantages discussed above. According to a first aspect of the present invention there is provided apparatus for removing piping from the ground, comprising an elongate flexible element and pipe engaging means fixed along the length of the flexible element, the pipe engaging means and the flexible element being insertable into a pipe in a first direction relative to the pipe and being arranged such that attempted withdrawal of the flexible element in the opposite direction to said first direction causes pipe engaging members of the pipe engaging means to engage the pipe and thereby prevent withdrawal of the flexible element, characterised in that said pipe engaging members comprise tubular sheaths, barbs, coil springs or wedges which extend outwardly from the elongate flexible element and which are adapted to be slidable against the surface of the pipe as the flexible element is inserted in said first direction, but which upon attempted withdrawal of the elongate element in said opposite direction contact the inner wall of the pipe such that friction generated between the pipe engaging members and the pipe causes the pipe engaging members to jam the flexible element in the pipe. With the apparatus according to the present invention, the force required to pull the pipe from the ground is distributed along the length of the pipe. The pipe engaging means may comprise barbs which extend from the flexible element at a plurality of locations along its length, the arrangement being such that said barbs permit insertion of the flexible element in one direction relative to the pipe but jam the flexible element in the pipe if withdrawal of the flexible element from the pipe is attempted in the opposite direction. The term "barb" used above and hereinafter is to be understood to mean a member which engages the pipe to resist withdrawal of the flexible element in one direction but allows the flexible element to be moved through the pipe in the opposite direction. The flexible element preferably comprises a multi-strand cable. The barbs may, for example, in this case be bound into the cable at a plurality of spaced apart locations along it's length. Alternatively the barbs may comprise springs or clips which are fixed onto the flexible element at spaced apart locations along its length. Preferably the flexible element is a multi-strand steel cable and the barbs comprise cable strands which have free ends projecting outwardly from the cable. In other words, the cable may effectively be frayed along its length to provide the barbs. Alternatively the flexible element may comprise a wire supporting brush strands (e.g. steel), the wire being woven into the core of the flexible element such that the steel strands protrude from the flexible element to form said barbs. As a further alternative the pipe engaging means may comprise cylindrical sleeves fixed at spaced apart locations along the length of the flexible element, and coil springs disposed around the cable between each adjacent pair of cylindrical sleeves, wherein each sleeve has an end tapering towards the cable such that attempted withdrawal of the cable from the pipe in said opposite direction to the direction of insertion causes an end of each coil spring to ride up the tapered end of a respective sleeve thereby forcing said end of each spring radially outwards thereby jamming the flexible element in the pipe. As a yet further alternative, the pipe engaging means comprises woven tubular sheaths disposed along the length of the flexible element, each sleeve having one end fixed to the flexible element between the flexible element and a surrounding collar, the arrangement being such that attempted withdrawal of the flexible element from the pipe in said opposite direction causes each sheath to bunch up ahead of a respective collar and thereby jam the flexible element in the pipe. According to a second aspect of the present invention there is provided a method of removing piping from the ground using the above apparatus, wherein the elongate flexible element and pipe engaging means are first inserted into a pipe in a first direction, the flexible element is then pulled in the opposite direction to said first direction so as to cause the pipe engaging means to jam the flexible element in the pipe, and the pipe is removed from the ground by further pulling of the flexible element in said opposite direction. Preferably the inserted end of the flexible element is passed through the entire length of the pipe to be removed and is coupled to an end of a new pipe which is to replace the pipe being removed so that the new pipe is drawn into position by the flexible element as the old pipe is pulled from the ground. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figs. 1 to 6 respectively illustrate six different embodiments of apparatus according to the present invention. Referring to Fig. 1, the illustrated cable (only a short length of which is shown) comprises a multi-strand steel cable 1 into which steel barbs 2 have been woven at regular and frequent intervals along its length. In use, to remove a water distribution pipe from the ground, a pipe 3 to be removed is first exposed by excavation and is isolated from the supply system in accordance with known methods. A length of cable 1 is then fed down the length of the pipe 3 in the direction of arrow A with the barbs 2 pointing in the opposite direction to the direction of insertion. The cable 1 may be fed into the pipe 3 in a number of ways which will not be described in detail here. For instance, the cable could be fed from a coiled supply by a power driven spinner machine in accordance with known methods which are used to feed wire cables through pipes in existing pipe removal systems. Such a spinner machine rotated the cable as it is driven forwards to ease it's passage through the pipe. The cable 1 is fed along the pipe 3 until the inserted end of the cable reaches the far end of the pipe 3 (not shown). The cable may either be fed into the pipe from the end of insertion, or drawn through the pipe, for instance using a steel cable drawn by a winch at the opposite end of the pipe. The opposite end of the cable 1 is then connected to a winch (not shown) which is used to pull the cable 1 in the opposite direction to that in which it was inserted into the pipe 3, i.e. in the direction of arrow B. When pulled in this direction, the barbs 2 engage the inner wall of the pipe 3 thereby distributing force between the cable 1 and the pipe 3 along the whole length of the pipe 3 and thus the pipe 3 is pulled from the ground. Because the pulling force is distributed to the pipe 3 along its whole length the problems encountered in existing methods in which the pulling force is concentrated at a single coupling between the cable and the pipe do not occur. Once the pipe 3 has been removed from the ground the cable 1 can be drawn out of the pipe 3, simply by pulling the cable out of the pipe 3 in the same direction relative to the pipe 3 in which it was first inserted into the pipe, and thereafter be re-used. It will be appreciated that whilst it is preferable for the cable 1 to be fed along the entire length of the pipe 3 so that as the pipe 3 is removed the pulling force is distributed along it's entire length, this may not be necessary in all cases. For instance, feeding the cable through only half, or some other portion, of the length of the pipe may be sufficient to distribute the pulling load adequately to enable removal of the pipe without the pipe breaking or distorting. The amount of cable which must be fed into any given pipe will depend upon a number of factors including the length, weight per length, and material of the pipe in question, and the local ground conditions. Prior to feeding the cable 1 into the pipe, a die former may be pulled through the pipe to pre-form it and ensure that it has the necessary cross-section along its length. This pre-forming operation could be a distinct preliminary operation or alternatively the die former could be fixed to the cable 1 ahead of the pipe engaging means. In a modification of the above described pipe removal method, the cable is fed along the entire length of the pipe to be removed so that the inserted end of the cable emerges from the far end of the pipe. This end of the cable is then coupled to a new, typically plastic, pipe which is then drawn into position in the location of the existing pipe as the existing pipe is itself being pulled out of the ground. Any suitable form of coupling could be used and thus further details will not be given here. It will be understood that the number of barbs 2 provided along the length of cable 1 may be varied considerably. Testing and experience will readily demonstrate the arrangement of barbs necessary for any given application of the cable. It will also be understood that the cable and/or barbs may take a wide variety of forms. Three possible alternative structures are shown in Figs. 2, 3 and 4 respectively. Fig. 2 illustrates a synthetic multi-strand cable 4 to which barb members 5 are fixed at various intervals along it's length. Fig. 3, illustrates a multi-strand steel cable 6 which is frayed at various points along it's length, the frayed strand ends 7 forming the barbs. The structure of Fig. 4 is similar to that of Fig. 3 in that steel strand ends 8 protrude from a cable 9 to form the barbs, but in this case the strands 8 are wound into a brush wire 10 which is woven into the core of the cable 9 such that the strands 8 protrude through that cable. In addition, whereas in Figs. 1 to 4, the various barbs project from the respective cables in a number of different radial directions, this need not necessarily be the case. For example, the barbs could be confined to a single plane to, for instance, more readily facilitate coiling and safe handling of the cable. As mentioned above, the barbs could take a wide variety of forms and be provided in any appropriate way either as an integral part of the cable 1 or as a subsequently added component. The only conditions which limit the configuration of the barbs are that they must allow the cable to be fed through the pipe in one direction but present substantial resistance to removal of the cable from the pipe in the opposite direction. Referring to Fig. 5, a fifth embodiment of the present invention is illustrated which comprises spaced apart sleeves 11 fixed to a cable 12. The sleeves 11 are generally cylindrical, each having a large diameter end (which has a maximum diameter slightly less than the internal diameter of a pipe 3 into which the cable is to be inserted) and an opposite tapering end which narrows towards the cable 12. Disposed between each adjacent pair of sleeves 11 are respective coil springs 13, each one of which extends from the large diameter end of one sleeve 11 to the tapered end of an adjacent sleeve 11. The arrangement is such that the cable 12 may be inserted into a pipe 3 in a direction indicated by arrow D in Fig. 5, i.e. with the large diameter end of the sleeves entering the pipe 3 first. During insertion any friction between the springs 13 and the inner wall the pipe 3 will tend to push the respective ends up the springs 13 down the tapering ends of the sleeves 11 and away from contact with the inner wall of the pipe 3. Once the cable 12 has been inserted the required distance into the pipe 3, withdrawal of the cable in the opposite direction to insertion causes respective ends of the coil springs 13 to ride up the tapered ends of the sleeves 11 and thus jam in between the sleeves 11 and the inner wall of the pipe 3 thereby securing the cable 12 in the pipe 3. The pipe 3 can then be removed from the ground whereafter the cable can be readily dislodged from the pipe 3 by simply pulling the cable through the pipe in the direction of original insertion. Another embodiment of the invention is illustrated in Fig. 6. A cable 14 has a number of relatively short tubular woven sheaths 15 spaced apart along its length. One end of each sleeve 15 is secured to the cable 14 between the cable 14 and a respective tubular sleeve 16. In use, the cable 14 may be inserted into a pipe 3 in a direction indicated by arrow E during which insertion the unsecured ends of each sheath 15 simply follow the respective sleeves 16 into the pipe 3. However, on attempted withdrawal of the cable in the opposite direction a combination of a friction between the sheaths 15 and the inner wall of the pipe 3 and the presence of the sleeves 16 causes the free end of each sleeve 15 to bunch up and thereby jam the cable in the pipe 3. Again, once the pipe 3 has been pulled from the ground the cable 14 can readily be removed from the pipe 3 by pulling it in the direction of original insertion.

Claims: Apparatus for removing piping from the ground, comprising an elongate flexible element (1;4;6;9;12;14) and pipe engaging means (2;5;7;8;10;11,13;15,16) disposed along the length of the flexible element, the pipe engaging means (2;5;7;8;10;11,13;15,16) and the flexible element (1;4;6;9;12;14) being insertable into a pipe (2;5;7;8;13;15) in a first direction relative to the pipe (3) and being arranged such that attempted withdrawal of the flexible element in the opposite direction to said first direction causes pipe engaging members (2;5;7;8;13;15) of the pipe engaging means (1;4;6;9;12;14) to engage the pipe and thereby prevent withdrawal of the flexible element (1;4;6;9;12;14), characterised in that said pipe engaging members (2;5;7;8;13;15) are adapted to be slidable against the surface of the pipe (3) as the flexible element is inserted in said first direction, but such that upon attempted withdrawal of the elongate element in said opposite direction friction generated between the pipe engaging members (2;5;7;8;13;15) and the pipe (3) causes the pipe engaging members to jam the flexible elements in the pipe. Apparatus according to claim 1, wherein said pipe engaging members comprise woven tubular sheaths (15) disposed along the length of the flexible element (14), each sheath (15) having one end fixed to the flexible element (14) between the flexible element (14) and a surrounding collar (16), the arrangement being such that attempted withdrawal of the flexible element (14) from the pipe (3) in said opposite direction causes each sheath (15) to bunch up ahead of a respective collar (16) and thereby jam the flexible element (14) in the pipe (3). Apparatus according to claim 1, wherein said pipe engaging members comprise barbs (2;5;7;8) which extend from the flexible element (1;4;6;9) at a plurality of locations along its length, the arrangement being such that said barbs permit insertion of the flexible element in said first direction but jam the flexible element in the pipe (3) if withdrawal of the flexible element from the pipe is attempted in the opposite direction. Apparatus according to claim 3, wherein the flexible element is a multi-strand cable (1) and the barbs (2) are bound into the cable (1) at a plurality of spaced apart locations along the length thereof. Apparatus according to claim 3, wherein the barbs comprise members (5) which are fixed onto the flexible element (4) at spaced apart locations along its length. Apparatus according to claim 3, wherein the flexible element is a multi-strand steel cable (6) and the barbs comprise cable strands (7) which have free ends projecting outwardly from the cable (6). Apparatus according to claim 3, wherein the flexible element comprises a wire (10) supporting steel strands (8), the wire being woven into the core of the flexible element (9) such that the steel strands (8) protrude from the flexible element (9) to form said barbs (8). Apparatus according to claim 1, wherein said pipe engaging means comprises cylindrical sleeves (11) fixed at spaced apart locations along the length of the flexible element (12), and said pipe engaging members are coil springs (13) disposed around the cable (12) between each adjacent pair of cylindrical sleeves (11), wherein each sleeve (11) has an end tapering towards the cable (12) such that friction generated between each coil spring (13) and the pipe (3) upon attempted withdrawal of the cable (12) from the pipe (3) causes an end of each coil spring (13) to ride up the tapered end of a respective sleeve (11) thereby forcing said end of each spring (13) radially outwards and thereby jam the flexible element (12) in the pipe (3). A method of removing piping from the ground using apparatus according to any preceding claim, wherein the elongate flexible element and pipe engaging means are first inserted into a pipe in a first direction, the flexible element is then pulled in the opposite direction to said first direction so as to cause the pipe engaging means to jam the flexible element in the pipe, and the pipe is removed from the ground by further pulling of the flexible element is said opposite direction. A method according to claim 9, wherein the inserted end of the flexible element is passed through the entire length of the pipe and is coupled to an end of a new pipe which is to replace the pipe being removed so that the new pipe is drawn into position by the flexible element as the old pipe is pulled from the ground.

Inventors: AUSTIN GRAHAM ARTHUR, PRESTON NICHOLAS JASON JOHN, AUSTIN, GRAHAM ARTHUR, PRESTON, NICHOLAS JASON JOHN
Applicants: UNITED UTILITIES PLC
Application year: 1994
Main classification: F16L55
IPC codes: F16L55